终于解决了IE8不支持数组的indexOf方法_javascript技巧

var from = Number(arguments[1]) || 0;
from = (from < 0)
? Math.ceil(from)
: Math.floor(from);
if (from < 0)
from += len;

for (; from < len; from++)
{
if (from in this &&
this[from] === elt)
return from;
}
return -1;
};
}